Abrasive article



May 12, 1942. J. P. FENTON ABRASLVE ARTICLE Filed May 1, 1941 R 3PM RM. LQJ+ INVENTO MW 5? x BY ATTORNEY Patented May 12, 1942 ABRASIVE ARTICLE John P. Fenton, Boston, Mass, assignor to American Sandpaper Company, a corporation of Massachusetts Application May 1, 1941, Serial No. 391,303

3 Claims.

The invention relates to an abrasive article essentially adaptable for grinding and finishing, y power drive, generally concaved or irregular surfaces such as holes and channels in metal. or composition parts, including oil reservoirs in steel forgings; also irregularly concaved surfaces such as occur in castings and compression molded parts; likewise the removal of scale, grime, and waste from such concavities.

Such grinding and finishing has heretofore been only imperfectly possible, and at great expense of time and material, by the use of such tools as shaped abrasive stone, buffs using abrasiive compounds, and hand work with coated abrasive sheets. Solid abrasive shapes are undesirable ior the work for the reason that the hardness of the tool will not allow it .to grind or finish smoothly, but rather causes violent short strokes which beat upon the work and result in imperfect finish, and cause what is known as chatter marks. The solid abrasive tool after a short time so wears down as to lose its shape, and consequently can no longer be used for the desired purpose. Attempts to provide resiliency in these shapes so as to overcome chatter, by making a bond between the abrasive grains of some compressible material, such as rubber, have been unsuccessful because such bond will not grip the abrasive grain sufficiently, and loose grains from the tool are ground into the work, causing grooves and scratches. Buffs using abrasive compounds either grind loose grains against the work in a similar manner, or are too fine in their finishing action to perform satisfactorily in a reasonable length of time. Hand work is so slow as to he usually impractical because of cost, and frequently holes or depressions are too small to permit successful finishing by hand.

The object of my invention is to provide an abrasive tool capable of producing an improved quality of work under the circumstances above outlined, and to obviate the dimculties referred to.

The invention comprises an abrasive article of replaceable character applicable to a mandrel upon which it may be mounted, and to which it may be secured so as to be rotated by the mandrel as the mandrel is rotated. The abrasive article is one in which the coated abrasive material is pre-formed in its fore part to have a generally convex form with vaulted interior, and this is so supported that it may be mounted upon the mandrel which will afford a resilient backing therefor, especially to the vaulted interior of the convexed part of the article; and to which mandrel the abrasive article is securely bound so as to be rotated thereby as the mandrel is rotated. The article is also one so fitted as to be capable of eliminating grindings or dust from any hole or opening within which it may be working. -These,

- been cut, or died out, and prior to its being are preferably spaced arms.-

formed, or molded, into the shape it assumes in the completed article.

Fig. 5 is a modification in the cut of theabrasive material shown in Fig. 4; and

Fig. 6 is a side elevation of the completed abrasive article when made from abrasive material with cut as shown in Fig. 5.

Fig. 7 shows in, cross section a slightly modified structure.

The abrasive article comprises various elements including a disk I, arms 2 extending from said disk. and an internal sleeve 3 over whichthe arms are extended and to which the arms are secured.

The disk I is a generally round, relatively flat, though preferably slightly convexed piece. It forms the fore end of the article, .and is located centrally with relation to its axis. The arms 2 They extend from all around the edges of the disk, first with an outward broad convexity which. gives to the fore part of the article its generally convex form and vaulted interior. Afterreaching the point where the arms impart to the article'its iull diametric size, thearms extend with a generally tubular extension substantially parallel with the axis of the article, which extension is continued onto the internal sleeve 3, to the exterior ofwhich the arms are secured. The sleeve thus occupies a slight inward extension, commensurate with the thickness of the material from which the sleeve is made, from the annular plane within which those portions of the arms secured to the sleeve are lying. As previously explained, the arms are preferably spaced arms, and the spacingis continued over the exterior of the sleeve.

The disk and arms are cut or died out from a blank or sheet of a flexible coated abrasive material, preferably such as a strong but flexible abrasive cloth; or coated abrasive which has a cloth backing. when out or died out the disk and arms have the general form in the flat as shown in Fig. 4 where it will be seen that the arms radiate from the edges of the central disk. The arms are then given the desired convex shape, without overlapping, and held in that shape by bonding to the sleeve I. The shaping is done by any suitable pre-forming device, or mechanism. p

The sleeve 3 may be made of any suitable material provided it hasthe requisite inherent stead of being substantially parallel to the axis strength to withstand thestirain to which it is subjected. A sleeve formed of paper, or cardboard, as known to those skilled in the art, is found in practice to be a'suitablegsleeve.

The abrasive is secured to its backing, and the arms to the sleeve, by a strong adhesive which will withstand a high degree of heat.' Some of the known heat treated resinous adhesives are found in practice to be best for the purpose.

The abrasive article is rotated by mounting upon a rubber mandrel 5, or one composed of such material as will provide a proper support I for the article and resilient backing therefor. "The mandrel is so formed that the abrasive article will fit over it, with the end of the mandrel fashioned to fill the vaulted interior of the article.

The mandrel is then expanded in such manner that the whole abrasive article will fit snugly thereon, although the strain induced by the expansion of the mandrel, for holding the article in place, is more or less concentrated upon the sleeve 3, thus relieving the arms of excessive strain, but providing them, especially those portions of the arms lying between the sleeve and the disk I, with a firm,- though resilient, backing.

Inasmuch as the abrasive surface material is securely bonded to its backing there is no tendency for the abrasive grains to pry loose. Since the abrasive coat is only one layer thick therecan be practically no loss of shape in use; as soon as the abrasive article placed upon the rubber mandrel is worn out it is replaced with a new abrasive article.

The abrasive article will operate successfully at either high or low speed, andwill withstand most severe abuse as may be encoimtered in any finish grinding with abrasives, as in the finishing of oil well bearing holes in the steel propeller hubs of air planes. Since the abrasive article is flexible in itself, and while at work is backed by a resilient mandrel, it is able to hug the surface being abraded, or finished, without chatter.

vDuring the operation of the abrasive article the grindings, together with bits of worn abrasive,

and dust, will be forced out of the concavity or groove within which the article is working, escap-- during its rotation.

abrasive article is' shown in that the sleeve 3 is extended into the vaulted end of the article by a part I which assists in further reinforcing the arms I, the spacing 6 between the arms being maintained the'same as before.

Iclaim: v

1. An abrasive article comprising a fiexible abrasive material fashioned to form an end piece centrally disposed with arms projecting from and around said end piece and convexed to impart a general convexity to said abrasive article in the part thereof bounded by the convexity in said arms and to which said end piece-forms an apex, an interior sleeve over which said arms are extended whereby the abrading working surface thereof will be increased, and to which sleeve said arms are adhesively secured whereby they are retained and reinforced by the sleeve, said sleeve providing a bearing against which an interior mandrel may be expanded for holding said abrasive article in place during its rotation.

2. An abrasive article comprising a flexible abrasive material fashioned to form an end piece centrally disposed with arms projecting from and around said end piece and convexed to impart a general convexity to said abrasive article in the part thereof bounded by the convexity in said arms and to which said end piece-forms an apex, an interior sleeve over which said arms have a generally tubular extension and to which sleeve said arms are adhesivelysecured whereby they are retained and reinforced by the sleeve, said sleeve providing a bearing against which an interior mandrel may be expanded for holding said abrasive article in place during its rotation.

3. An abrasive article comprising a flexible abrasive material fashioned to form an end piece centrally with arms projecting from and around said end piece and convexed to impart a general conveidty to said abrasive article in the part thereof bounded by the convexity in said arms and to which said and piece forms an apex, said arms having a g fl' y tubular portion beyond the convexed portionthereof, a sleeve located inside said generally tubular portion of said arms with extension into the vaulted interior of the convexed portion thereof, and to whichsleeveandextensionsaidarmsaread-.

hesively secured whereby they are retained and reinforced thereby. said sleeve providing a hearing -against which an interior mandrel may be extended for holding said abrasive article in place JOHN P. FENTON. 

